1. Field of the Invention
The invention relates to a residual pressure holding valve and to a suspension strut with such a residual pressure holding valve, in particular for a motor vehicle.
2. Description of the Related Art
The invention can be applied to any vehicle, but will explained in detail, along with the problems on which it is based, with respect to a passenger motor vehicle.
Hydropneumatic suspension systems in motor vehicles permit the spring system to be adapted in a convenient, fast and versatile fashion to conditions of the roadway, the payload of the motor vehicle and/or the driving properties of the chassis of the motor vehicle desired by a vehicle driver. The spring effect of such a suspension system is ensured by gas-filled spring bellows, and the gas pressure within the spring bellows can be adjusted using, for example, a compressor. Pressure holding valves are used to maintain the functional capability of the spring system in the event of a pressure loss, for example due a failure of the compressor or a leak in the pneumatic system. The pressure holding valve prevents air from being able to flow out of the spring bellows. A sufficient residual holding pressure therefore always is maintained in the spring bellows.
DE 198 54 540 C2 describes such a pressure holding valve. The pressure holding valve has a pump-end housing component and a consumer-end housing component that are plugged into one another in certain sections and that have an inflow and an outlet. A flexible rubber diaphragm is arranged between the housing components to separate the inflow from the outlet in a gastight fashion. A diaphragm face of the rubber diaphragm is loaded with the air pressure when an air pressure is applied to the inflow. As a result, a sealing face of the diaphragm is lifted from a valve seat of the pump-side housing component counter to the force of a valve spring. The operating pressure may drop below a threshold value predetermined by the valve spring if, for example, the pumping capacity of the compressor drops. As a result, the sealing face of the diaphragm comes to rest again on its valve seat However, the housing components of this arrangement are very complex and costly to fabricate, and the presetting of the residual holding pressure by the valve spring, which acts counter to the inflow air pressure, only can be adjusted very imprecisely.
The present invention therefore is based on the object of providing an improved residual pressure holding valve that eliminates the abovementioned disadvantages.